College Hill has taken on a corporate media relations brief to support the firm's brand-building and business development efforts in the UK.
The agency won the brief via a competitive four-way pitch. Spada, which formerly held the six-figure account, is thought to have not repitched for the business.
The brief comes after a period of intense speculation over the future of the global real estate firm.
After the pitch began earlier this year, DTZ replaced both CEO Paul Idzik and finance director Robert Rickert in August.
The company is also subject to a number of bids, including a merger with French-owned property group BNP Paribas, which was expected to have been rubber-stamped in July but remains unresolved.
Anna Reid, DTZ's head of group media relations, said that College Hill's brief was 'completely separate' from the group-level situation.
She said: 'Takeover talks may or may not result in something concrete. I don't think you can put your business on hold and wait for that outcome. In the meantime, there's a job to do and we are carrying on doing it.'
The firm has contracted College Hill on a retained basis. The firm also uses Blythe Weigh Communications for financial PR.
Reid said that College Hill's brief differed slightly from that of the incumbent, as Spada performed more of an outsourced press office role before the company built up its in-house offering.
College Hill will provide creative support to the in-house team, including social media advice.
Victoria Cross, associate partner at College Hill, will lead the team.